The subject invention relates to nonrotatably connected telescoping driveline assemblies for heavy vehicles. Current driveline assemblies include splined male and female members which are nonrotatably connected to transmit rotational movement from one member to the other. Typically, the female member drives the male member. The driveline assemblies also permit relative longitudinal movement between the male and female members. In other words the male member can slide or slip within the female member to facilitate assembly and disassembly as well as assisting in absorbing exterior forces. The exterior forces are usually created by movement of the vehicle over a road surface.
The female member is typically attached to a yoke and includes a number of internal substantially rectangular splines. The female member is machined from ductile iron castings, forgings or bar stock and requires spline broaching, drilling and tapping along with outside diameter turning.
The male member is also typically attached to a yoke or tube and has a number of external substantially rectangular splines. The external splines are made from forgings and require turning, hobbing, hurth milling, or rolling to achieve the appropriate sizing. In addition, the external splines require induction hardening and a polyglide coating.
The splines of the male member slideably engage the splines of the female member. Hence, the male member can slide or slip within the female member; however, the male member must not be too loose as to affect the balance, vibration, or overall performance of the vehicle. Accordingly, the sizing of the internal and external splines must be closely controlled.
The splines must facilitate the nonrotatable connection and must also exhibit a close tolerance fit to minimize backlash in the transmission of torque from one member to the other. The close tolerances required between the splines is one of the primary difficulties encountered when fabricating these prior art drivelines. The machining operations listed above must take into account various factors which affect the tolerances between the splines and the other parts of the male and female members. These factors can include variations in wall thickness, roundness, and temperature variations. As can be appreciated, machining these members and maintaining the specific tolerances required between the splines for a close metal to metal fit is extremely difficult, expensive and time consuming.
Many designs for nonrotatable telescoping male and female members are known in the prior art. One such design has been proposed for a steering shaft application. In this application, a tube assembly has male and female members with end portions slidably engaged within one another. The male and female members are hollow tubes which have a number of teeth formed along an end portion thereof. The male member is designed smaller than the female member and a void space is formed between the male and female members.
An elastomeric sleeve is injected into the void between the male and female members to nonrotatably connect the male and female members with a minimum amount of relative rotation therebetween. Specifically, the sleeve is adhered to an inside surface of the female member and has a shape complimentary to the outside surface of the male member. The sleeve serves as a tooth size control and as a wear surface for any slipping forces encountered. There is a degree of shrinkage when the elastomeric sleeve cools from an injection temperature to an operating or ambient temperature which allows the male member to slide within the female member. The sleeve assists in reducing backlash and creates an adequate tolerance between the male and female members. This design is effective in reducing the overall weight of the steering tube assembly, improving the fit between the male and female members, reducing the overall manufacturing costs, and increasing manufacturing efficiency. This type connection, however, has not been proposed for use in heavy vehicle drivelines.
Each of the teeth in this type of prior art connection include an outer surface and a pair of legs. The legs of the teeth are directly connected to each other. Hence, the inner surfaces of both the male and female members have a number of V-shaped legs extending outwardly to the outer surfaces. This configuration of teeth appears to operate effectively when utilized in a steering tube assembly. However, if this configuration was enlarged to the size of a typical driveline, the design would not be able to withstand the rotational forces or torque between the two members. Specifically, the legs of the teeth on the female member might operate as ramps for the legs of the teeth on the male member. Thus, one potential deficiency with this known design is the V-shaped interior of the male and female members and the size of the teeth in relation to the overall diameter of the members.
Accordingly, there exists a need for a heavy vehicle driveline assembly that incorporates the advantages of hollow or thin walled male and female members with a custom fit sleeve. Further, there is a need to overcome the deficiencies of the tooth design disclosed above.